2001 Duramax LB7 Knocking

[rpaoness]

Current score - 6/8 manifold-to-head bolts removed. I have had to weld on and break off more washers and nuts then I think on any other project to date. Access is really bad so it's hard to get a "good" weld. I bought CRC freeze-off from Autozone, hoping that would help. I don't know if it has or not, but I got two of the 4 most stubborn ones out this morning since I bought it and tried it...

[rpaoness]

Got all of the remaining bolts out last night and finished installing the new manifold this morning. Still has a nasty wrap or knock but no exhaust leak noise. I’ll have to do something to improve my troubleshooting. Smoke and earlier failed emissions tests indicated a failing injector. A real hole in the exhaust manifold indicated failed manifold. Now that those are corrected I wonder how to troubleshoot knock. Pull valve covers and look at rockers first? That requires removing injector lines, temporarily reinstalling…

[rpaoness]

Oil pressure is still 80 psi on startup. I wonder if I should let it warm up fully to see if it improves

[rpaoness]

Seems quieter after running it. Only evident when at low load/part throttle. Goes away under heavy acceleration. Still have 45psi oil pressure at idle. No sign of blow by. My guesses are valve train noise or a noisy new injector. If it’s an injector it might go away. Or a lifter stuck after sitting for 2 months might also clear up. But I seem to never ever be that lucky.

[rpaoness]

Apparently there’s a very common “typewriter” tick that there are even tsb’s about it.

[kevm14]

Well ticking isn't knocking.

[rpaoness]

It is most evident below 1500 rpm and blower max or radio can almost mask it.

[kevm14]

Based on what you have described it seems safe to run it and just monitor.

[rpaoness]

Yeah - I think. I have been worried about partially kinked fuel hoses resulting in low rail pressure since I put on custom stainless lines with slightly incorrect hose crimp orientation in the two rubber sections. I should cut those off and reorient, just in case the suction pressure is hurting injector performance. I could also ask the injection shop I bought the injectors from to listen to it to get their opinion. But I’d want to fix the suction line before I brought it there anyhow.

[rpaoness]

Realigned the fuel hoses so there are way fewer kinks. Pumping the priming pump by hand while idling seems like it might be changing the noise slightly? I wonder if I have either a lazy injector (they were Bosch authorized remans) or a weak/marginal cp3 high pressure pump. I would’ve thought a marginal cp3 would set a fuel pressure response related code. There was some check engine light code when I first started after injectors, but it went away after 2 or 3 drive cycles.